There are several known tools for assisting snipers or long-range shooters in arriving at a firing solution. A firing solution can be seen as the result of a series of complex mathematical equations that a shooter can perform to arrive at an appropriate elevation and windage adjustment for a target at a given distance.
Known software-based tools currently used by shooters in the field are referred to, or commonly known as, ballistic computers and/or ballistic calculators. They can function within a full-size computer, handheld computer, PDA, mobile phone, and the like. Ballistic computers require the shooter to enter precisely gathered data referring to the specific attributes of a system which is to be fired, in addition to atmospheric data, such as air temperature, barometric pressure, altitude, humidity, and the like.
Ballistic computers and associated ballistic programs rely upon these precisely gathered and entered variables to compute an accurate measure of the true or “net” air density, commonly known as density altitude. Computing the density altitude allows them to predict the amount of vertical and horizontal compensation required to fire a projectile through a given measure of air density or “density altitude” at targets of varying distances. Known ballistic computers can provide highly accurate firing solutions but include significant disadvantages as they are battery-powered, software-driven, and are subject to fail in harsh environmental conditions due to loss in battery power, rough handling, or various other reasons. Software-based ballistic computers and programs are complex in nature and require the user to have an advanced understanding of exterior ballistic science and associated theories, thus requiring the user to continually practice using the program in order to maintain proficiency in its efficient and effective use. This complexity is not advantageous to military snipers operating under stress and time constraints found in combat environments and situations. Ballistic computers can also be costly to purchase, update, repair, and can take up valuable space in a shooter's pack and/or add weight to an already heavy load commonly carried in austere combat conditions.
Other known non-software based tools currently being used by shooters include analog slide-rule type devices. These tools allow a shooter to compute the distance to the target as well as a rough firing solution based off of a ballistic chart, see for example, U.S. Pat. No. 5,960,576 and U.S. Pat. No. 6,196,455. However, such known analog-type devices are flawed in that they do not determine a firing solution by compensating for the current value of density altitude in which the fired projectile is to travel through. Instead, they operate by using a fixed and standardized air density value, commonly known as Standard Atmospheric Conditions, or another set of preset and fixed atmospheric conditions. As a result, known analog-type devices do not allow a shooter to make adjustments based upon the current density altitude nor can they make adjustments as the density altitude value changes. By not compensating for the current density altitude, known non-software based tools experience a significant loss of accuracy when determining a firing solution across a wide range of environmental conditions.
Another known non-software based tool currently used by shooters is a reticle system. This known system includes a density altitude measurement graph that is incorporated as part of the reticle within the scope of the firearm, see for example, U.S. Pat. No. 7,748,155. In use of this system, the user estimates the density altitude using the graph within the scope and then selects a corresponding aiming point on the reticle that provides appropriate trajectory compensation for a bullet fired at a specific muzzle velocity. The reticle system is only functional to the user if the user has in their possession a scope that has the proprietary aiming system built into the internal lens system. This aiming system is also fixed within the scope of the firearm and requires the user to possess ammunition that has a muzzle velocity that matches the calibration of both the reticle and the aiming system within the scope.
Accordingly, there exists a need for a simple and reliable tool for assisting snipers or long-range shooters in arriving at very accurate firing solutions by compensating for the actual measure of air density being fired through. Such a tool should be usable with any type of firearm sight, scope, or aiming system and capable of being tailored to a user's specific equipment performance parameters. There also exists a need for a tool which is small, affordable, and extremely resilient to rough handling and harsh environmental conditions, while not requiring a source of power, such as batteries or a power outlet, or forming a part of the firearm sight, scope, or aiming system.